WebBrowswer1.DocumentText = TextBox1.Text

That solves the problem

Also, you can apply source-formatting buttons by doing this:

Create a button, "Make Text Bold" ... When this button is pressed, have it perform the following action

TextBox1.SelectedText = "<b>" & TextBox1.SelectedText & "</b>"

This will add HTML bold tags around whatever is selected.

Hope this helps!

Jonathan